If you still believe that athletes need to consume diets high in carbohydrates and sugars before and during competition and training, you are living in the past. The research that you are basing this assumption on is old and likely funded by the Gatorade Sports Science Institute. Not only can athletes perform at elite levels on low carbohydrate diets, but often receive performance enhancing benefits of converting their metabolism to burning fat!

Early adopters of low carbohydrate/high-fat diets are currently setting course records and dominating the competition. Athletes like Timothy Olson, Ben Greenfield, and LeBron James are just a few recognizable names that have taken a leap of faith and modified their diets counter to the high carbohydrate sports science. Once fully adapted, these high-fat athletes have a seemingly endless fuel tank, improvement in mental focus, and a decrease in body fat.

epic_timothyolson31Timothy Olson is a prolific professional ultra mountain runner and a whole foods/high fat athlete.

To realize the full potential of low carbohydrate diets, a metabolic adaptation known as ketosis must take place. This occurs when carbohydrates are limited to below 50g/day and dietary fat is significantly increased. On a metabolic level, our body converts from a sugar burning machine into a fat burning beast! This process of burning fat as a primary fuel source unlocks a myriad of physiological adaptations that favor athletes.

In an effort to help you understand the basic physiology and science behind low carbohydrate diets, these are the primary benefits of fully keto-adapted athletes.


In carbohydrate dependent athletes there is competition for limited glycogen stores between skeletal muscles and the brain. Skeletal muscles are larger and will utilize glycogen to exhaustion. This causes the non keto-adapted athlete to bonk!

  1. Superior Brain Fuel– Bonking sucks! I call it "transcending time and space" as well as "running with the buffalo spirit". It happens when your body runs out of available sugars (glycogen) to produce energy. At any point in time a sugar burning athlete can maximally store around 2000 calories of glycogen. In a keto-adapted athlete, the body does not rely on this limited fuel source but instead utilizes the over 40,000 calories of stored fat! In a fat burning athlete, you will not bonk!

–Maintaining mental focus

  • Carbohydrate dependent athlete will eventually exhaust liver glycogen reserves
  • Muscles and brain compete for small amounts of glucose derived from gluconeogenesis from protein

–Protecting athletes from hitting the wall

  • Bonking, blowing up, running with the buffalo spirit, transcending time and space


Fat utilization is much higher in a low carbohydrate athlete! Sugar burning athletes rely on sugar as fuel and spare energy dense fat.

  1. Improved Body Composition- Counter to popular belief, consuming dietary fat does NOT make you fat. In fact, if you consume a diet low in carbohydrates and high in dietary fat you are likely to significantly decrease body fat while building lean muscle mass. This is accomplished due to improvements in insulin sensitivity.–Decrease fat while maintain or build muscle
    • Increased quickness, agility, and performance

    –Maintain specific body weight for sport

    • Wrestling, boxing, powerlifting, martial arts
    • Bodybuilding, gymnastics, dance, fitness modeling

    –Improved self-perception

    Better mental state going into competition

  2. Improved Exercise Recovery- Keto-adapted athletes have shorter recovery times and thus can train harder and longer than their sugar burning counterparts. Obvious training advantages that translate to superior conditioning on race day!–Fat oxidation lessens the stress response to exercise–Less metabolic stress
    • less inflammation, immunosupression, gastro-intestinal distress, muscle damage, soreness

    –Less generation of reactive oxygen species

    • Preservation of highly unsaturated fatty acids in cell membranes
  3. Improved Digestion and Nutrient Absorption- One of the most frequent causes of a bad race day is gastro-intestinal distress. Because sugar burning athletes have a limited supply of glucose, they are required to constantly replenish glucose during exercise. Consuming high levels of carbohydrates and sugars for hours on end is very difficult on the stomach and can cause serious pain and discomfort. This unpredictable fuel source is exponentially more unreliable when you introduce altitude or increase intensity. When you body burns fat as a primary fuel source, you can avoid constantly consuming foods during exercise (remember, your body can store up to 40,000 calories of ready to mobilize fat!). This fat burning system spares the stomach and leads to more glorious days!–Fat oxidation is a sustainable and reliable fuel source for skeletal muscles
    • No gastro-intestinal distress

    –Ketones are a sustainable and reliable fuel source for the brain

    • No bonking


A keto-adapted athlete has enough accessible fuel to run for over 48 hours straight without fuel!

To learn more about the science behind ketogenic diets and the ergogenic improvements for athletes, read The Art and Science of Low Carbohydrate Performance. It is the book that both Katie and I have used to guide us into nutritional ketosis and has led to our most successful race seasons!


The bible for anyone looking to learn more about ketosis and training!


Ketogenic diets offer a slew of health benefits that are not limited to athletes! In fact, the performance benefits mentioned above translate into real life, ass kicking advantages for anyone that modifies their diet! Ketogenic diets have been shown to effectively stop certain types of cancer, treat obesity and help with weight management, as well as cease diabetic symptoms! Read Keto Clarity by Jimmy Moore to learn more about the overall benefits of a ketogenic diet!

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